Electromagnetic induction-based direct melting can rapidly melt metallic materials, thereby ensuring high yield with minimized contamination of raw materials. The electromagnetic induction-based direct melting is generally performed according to the following principle.
When an alternating current is applied to an induction coil wound around a crucible to induce magnetic field variation, an induction current is created on the surface of metal to be melted and generates Joule's heat, which melts the metal. Further, the induction current interacts with a magnetic field to generate the Lorentz force in molten metal.
Since the Lorentz force is always directed toward an inner center of the crucible and provides a pinch effect or electromagnetic pressure effect according to Fleming's left hand rule even when the direction of the current in the coil is varied, it is possible to prevent the molten metal from contacting an inner wall of the crucible.
However, the electromagnetic induction melting cannot be applied when melting semiconductors such as silicon. That is, since silicon has a very high melting point of 1,400° C. or more and a very low electric conductivity at 700° C. or less unlike metals, it is difficult to achieve direct electromagnetic induction-based silicon melting.
When melting the semiconductors such as silicon, indirect melting with heat from a graphite crucible is generally used. Although graphite is a non-metallic material, it has very high electric and thermal conductivity, thereby allowing the crucible to be easily heated through electromagnetic induction. When producing a SiOx nanoparticle using a molten silicon melted in such the graphite crucible, there is a limit in using entire molten silicon for manufacturing SiOx nanoparticle so that molten silicon residue on the inner bottom surface of the crucible may not exist. After SiOx nanoparticle is manufactured from molten silicon, there may be molten silicon residue inside the crucible. The molten silicon residue causes problems such as acting as a source of contamination of the molten silicon if reused after the end of reaction and shortening the life of the crucible for melting silicon due to cracks of the graphite crucible caused by a volume expansion of molten silicon. That's because the molten silicon residue is stuck on the inner bottom surface of the crucible during the cooling process.
Related Prior Art is Korea Patent Publication No. 10-2010-0042489 (Apr. 26, 2010 published). The document does not disclose SiOx nanopowder manufacturing apparatus having a silicon melting crucible with the sliding type tapping structure and a SiOx nanopowder manufacturing method using the apparatus. In the document, only a graphite crucible for electromagnetic induction melting silicon and apparatus for silicon melting and refining using the graphite crucible has been disclosed.